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collapseos/blk/807
Virgil Dupras a7dcb522c2 Make br cells 1 byte wide
The 1 byte limitation has been effective for a while now, but I
hadn't made the move yet, I wanted to see if the limitation would
cause me problems. It doesn't.

Doing this now slightly facilitates the IY->BC move in z80.

Bootstrapping: if you try to recreate the CVM binary from the
previous commit with this code, you'll have bootstrapping problems.
The first bootstrap will compile a binary with 2-bytes wide cells
but branching conditionals that yields 1-byte cells. That's bad.

I got around the issue by temporarily inserting a "397 399 LOADR"
instruction in cvm/xcomp.fs, right before the xcomp overrides. This
way, I force 1-byte cells everywhere on the first compiliation,
which then allows me to apply the logic change in cvm/vm.c and have
a properly running binary.
2020-07-06 07:27:50 -04:00

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CODE (loop)
PC 0x47 - ORG @ 0x45 + ! ( stable abi )
[BP] 0 INC[w]+, ( I++ )
( Jump if I <> I' )
AX [BP] 0 MOVx[]+, AX [BP] -2 CMPx[]+,
JNZ, L1 @ RPCs, ( branch )
( don't branch )
BP 4 SUBxi, DX INCx,
;CODE